Night vision goggles, cameras and other imager devices are useful in a variety of low and no light conditions. From search and rescue operations to nocturnal animal viewing and hunting, night vision imaging devices can reveal the world around us in situations in which the use of artificial illumination is impractical, impossible or otherwise undesirable. Many conventional night-vision imaging devices use portions of the near and/or far infrared spectrum, thus making them potentially useful for thermal.
The potential thermal imager capabilities of night vision imaging devices can be incredibly useful when deployed in search and rescue operations. In such situations, night vision imaging devices can be used to detect body heat of injured or unconscious people or animals that fall victim to natural disasters or other catastrophes. Although it is possible to search for victims of large-scale accidents and disasters using conventional artificial light such as spotlights, visible light searches will not reveal the thermal signature of a warm body as night vision imaging devices can. Furthermore, since conventional artificial light sources can often introduce extraneous infrared light and heat onto a scene and thus overload or blind night vision imaging devices, the use of artificial light source while using night vision imaging devices is often undesirable.
Night vision imaging devices are also desirable in situations in which use of artificial light is undesirable because it can either interfere with, spook or alert subjects, such as animals, when they are being observed or hunted in lowlight and no light situations. For example, scientists, such as biologists and zoologists, may wish to observe the nocturnal activities of various animals and insects without disturbing or influencing their behavior with artificial lights or revealing the location from which the observations are being made. Hunters may also find such capability desirable when hunting wild game.
However, for as useful as night vision imaging devices can be for low light and the no light conditions, their use can be restrictive when the user of such devices is required to navigate through space or operate vehicles such as a car or helicopter. Typical night vision imaging devices, such as night vision goggles 100 shown in FIG. 1, have limited fields of view, providing little to no peripheral vision to the user of the night vision goggles 100, which can make operating vehicles difficult or dangerous. The lack of peripheral vision often found with night vision imaging devices can often necessitate using night vision imaging devices in teams in which one person uses the night vision imaging device while the other uses unaided or natural vision to navigate or operate vehicles or other equipment.
FIGS. 2a and 2b illustrate the differences between the perceptions of a scene as viewed through a night vision imaging device and as viewed with the unaided eye. Although scenes 200a and 200b are of the same location in space and at the same time, the differences between the scenes include differences in perceived illumination color, level of observable detail and field of view. For instance, scene 200a depicts a scene as viewed through a night vision image imager device. In this case, the night vision imaging device might be a pair of night vision goggles, in which case the field of view might be limited to a portion of the scene within the boundaries of area 225a. As can be seen, the area 225a is significantly less than the entirety of the scene 200a. However, the typical trade-off for narrow field of view is an increase in the amount of detail visible to the user in low light conditions. For example trees 205a and dog 210a are much more visible in the scene 200a as viewed through a pair night vision goggles than they are in the scene 200b viewed with an unaided eye. As shown in FIG. 2b, trees 205b and dog 210b are almost completely occluded by the darkness of night in scene 200b. The only details that can be seen in scene 200b are details with large amounts of visible light. In this case, the moons 215a and 215b in scenes 200a and 200b respectively, are readily observable in both scenes. In fact, moon 215b may be the only detail the viewer of scene 200b may be able to discern with the unaided eye.
In situations such as this, the limitations of the night vision goggle may render one user unable to operate certain equipment or drive a vehicle. To allow the user of the night vision goggles greater capability, he or she may be paired up with another team member who can operate machinery or drive a vehicle. To be an effective team, the night vision member of the team and the unaided vision member of the team must practice and train to work as a unit to use the night vision imaging device in whatever situation they might employ the use of the night vision imaging device.
To practice operating as a team, many schemes and apparatus have been developed. One such traditional training apparatus is shown in FIG. 2c. FIG. 2c depicts a system that can display both an infrared image and a visible light image on the screen 280 and display the images to two or more users at the same time. For example, projector 250V can be used to project a low level visible light scene onto screen 280, while at the same time projector 2501R can be used to project an infrared image onto screen 280. For purposes of illustration, the scenes 200a and 200b can be the scenes projected onto screen 280. The scenes 200a and 200b are essentially overlaid on top of one another, however, only user 2701R wearing a pair of night vision goggles can see the infrared information of scene 200a, while user 270V will only be able to see the visible light information of scene 200b. With such a setup, users 2701R and in 270V can practice interacting and cooperating with the scenes displayed on screen 280 while viewing the different information available in the two scenes projected in the visible and the infrared spectra.
Although such setups are useful, they are less than ideal. The use of two projectors, 250V and 2501R, presents many problems including, but not limited to, the increased cost of requiring two projectors, spatial alignments of the two images projected onto screen 280, temporal alignment of the signals being fed to the two individual projectors and potential visible artifacts that may occur when using two separate imager devices in the two projectors. Embodiments of the present invention, alone and in combination, address these and other issues.